a. It is assumed that your system has the proper received signal
level and that you and the other station are using low power; your sites are
masked from the enemy when possible by using terrain obstacles.

b. Systems that are parallel to the front lines are less open to ECM
than systems that are perpendicular. Division systems are more prone to ECM
than corps systems because of the proximity to front lines.

c. Multichannel systems should be separated from HF radios because
of the high power and resulting spontaneous and harmonic radiation. FM radios
should not be collocated with multichannel sets for the same reasons.
Collocated multichannel antennas should be either back to back or on-line to
reduce mutual interference. Antennas should never be in line with one
another.

d. The need for dispersion and the need for high mobility always
clash. To mask a unit's location, all radios including multichannel should
be separated from the command post by at least 2 kilometers (1.2 miles).
Cables should not be used to interconnect radios and the command post because
cable recovery is too time consuming. A radio link should be used when
available.

e. In most cases, the enemy prefers to monitor our systems even
though they are denied clear reception of our signals because of encryption.
An electronic signature of our unit's location is of better intelligence than
jamming. Multichannel systems indicate headquarters' locations. Their
presence indicates a stable nonmobile situation. We give the enemy valuable
signal intelligence when stations go off the air and then reappear elsewhere.
We are telling the enemy our situation is changing.

f. Determining if ECM is being used against your system is not easy
since most interference is from our own emitters.

g. Proper and diligent frequency management is imperative. When
interference occurs, submit the MIJI report. Do not change the frequency up
or down to get away from interference. This creates additional problems for
other users. Use tactical satellite instead of terrestrial line of sight when
possible.

D-2. Procedures

a. The following may indicate that your systems are being interfered
with either intentionally or unintentionally:

Subscribers report that trunks are noisy, or that the speech of
the other party is fuzzy or unintelligible.

Subscribers and switchboard operators report no contact with a
particular unit(s).

You are unable to make contact with the distant end on the
orderwire.

b. The following steps reduce or eliminate the effects of ECM or
mutual interference: